“…1). Of 27 publications that were considered potentially relevant[2,3,4, 8, 9,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33], 13 were subsequently excluded due to the reasons given in figure 1[14,18,19,20,21,24,25,26,27, 29, 30, 33]. Fourteen studies published between 1995 and 2006 met the inclusion criteria [2,3,4, 8, 9, 12, 13, 15, 17, 22, 23, 28, 31, 32].…”